Telecommunications apparatus and methods

ABSTRACT

A terminal device for use in a wireless telecommunications system comprises a transceiver to perform wireless communication with a base station and to obtain system information defining communication parameters from system information data received from that base station; system information storage; and a controller to detect whether the system information storage already holds at least some of the system information applicable to a newly communicating base station and to control the transceiver to obtain any portions of the system information not already held by the terminal device, in which: the system information comprises a plurality of system information blocks; and the controller is configured to detect parts of a system information block stored by the system information storage which are applicable to the newly communicating base station and to obtain other parts of that system information block as a partial system information block from the newly communicating base station.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.15/615,522, filed Jun. 6, 2017, which is a continuation of InternationalApplication No. PCT/EP2016/072200, filed Sep. 19, 2016, which claimspriority to European patent application 15193497.3, filed Nov. 6, 2015,the contents of each are herein incorporated by reference.

BACKGROUND Field

The present disclosure relates to telecommunications apparatus andmethods.

Description of Related Art

The “background” description provided herein is for the purpose ofgenerally presenting the context of the disclosure. Work of thepresently named inventors, to the extent it is described in thisbackground section, as well as aspects of the description which may nototherwise qualify as prior art at the time of filing, are neitherexpressly or impliedly admitted as prior art against the presentinvention.

The present disclosure relates to wireless telecommunications systemsand methods.

Mobile communication systems have evolved over the past ten years or sofrom the GSM System (Global System for Mobile communications) to the 3Gsystem and now include packet data communications as well as circuitswitched communications. The third generation partnership project (3GPP)is developing a fourth generation mobile communication system referredto as Long Term Evolution (LTE) in which a core network part has beenevolved to form a more simplified architecture based on a merging ofcomponents of earlier mobile radio network architectures and a radioaccess interface which is based on Orthogonal Frequency DivisionMultiplexing (OFDM) on the downlink and Single Carrier FrequencyDivision Multiple Access (SC-FDMA) on the uplink.

Third and fourth generation mobile telecommunication systems, such asthose based on the 3GPP defined UMTS and Long Term Evolution (LTE)architectures, are able to support a more sophisticated range ofservices than simple voice and messaging services offered by previousgenerations of mobile telecommunication systems.

For example, with the improved radio interface and enhanced data ratesprovided by LTE systems, a user is able to enjoy high data rateapplications such as mobile video streaming and mobile videoconferencing that would previously only have been available via a fixedline data connection. The demand to deploy third and fourth generationnetworks is therefore strong and the coverage area of these networks,i.e. geographic locations where access to the networks is possible, isexpected to increase rapidly.

The anticipated widespread deployment of third and fourth generationnetworks has led to the parallel development of a class of devices andapplications which, rather than taking advantage of the high data ratesavailable, instead take advantage of the robust radio interface andincreasing ubiquity of the coverage area. Examples include so-calledmachine type communication (MTC) applications, some of which are in somerespects typified by semi-autonomous or autonomous wirelesscommunication devices (MTC devices) communicating small amounts of dataon a relatively infrequent basis. Examples include so-called smartmeters which, for example, are located in a customers home andperiodically transmit data back to a central MTC server relating to thecustomers consumption of a utility such as gas, water, electricity andso on. Smart metering is merely one example of potential MTC deviceapplications. Other examples include vehicle communications systems (forexample, vehicle-to-vehicle (“V2V”), vehicle-to-pedestrian (“V2P”) orvehicle-to-infrastructure/network (“V2I/N”) systems, referred togenerically as “V2X” arrangements. Further information oncharacteristics of MTC-type devices can be found, for example, in thecorresponding standards, such as ETSI TS 122 368 V11.6.0 (2012-09)/3GPPTS 22.368 version 11.6.0 Release 11).

In MTC arrangements, including V2X systems, technical issues can arisein the provision (by a base station) or acquisition (by a terminaldevice) of so-called system information. In broad summary, systeminformation, or at least some aspects of system information, in existingwireless telecommunications systems, such as LTE-basedtelecommunications systems, is transmitted as System Information Blocks(SIBs). Receipt of the SIBs is required in order for a terminal deviceto be able to communicate with a cell, for reduced capability devicessuch as MTC devices, these SIBs can be large in comparison to the datahandling capabilities of the device. This can also be an issue in thecontext of vehicle-based devices, where the movement of the vehicle (andthe potential small size of cells defined, for example, by road-sideunits (RSUs) means that the time spent by a terminal device in aparticular cell may be short. Similarly, in the context of coverageenhancement, it is sometimes difficult for a terminal device (whetherreduced capability or not) to receive large SIBs. There is therefore aneed for schemes which allow system information to be communicated toterminal devices operating on restricted frequency resources in wirelesstelecommunications systems. There is also a need for schemes which allowsystem information to be communicated to terminal devices operating in acoverage enhancement situation.

It is a constant aim to improve the operation and efficiency of wirelessnetwork systems.

SUMMARY

The present disclosure can address or mitigates the problems discussedabove.

Respective aspects and features of the present disclosure are defined inthe appended claims.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary, but are notrestrictive, of the present technology.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the disclosure and many of the attendantadvantages thereof will be readily obtained as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings wherein likereference numerals designate identical or corresponding parts throughoutthe several views, and wherein:

FIG. 1 schematically represents an example of a LTE-type wirelesstelecommunication network;

FIG. 2 schematically represents some aspects of a LTE downlink radioframe structure;

FIG. 3 schematically represents some aspects of a LTE downlink radiosubframe structure;

FIG. 4 schematically illustrates a base station;

FIG. 5 schematically illustrates a terminal device;

FIG. 6 is a schematic diagram showing a controller of a terminal device;

FIG. 7 schematically illustrates system information storage;

FIG. 8 is a schematic flowchart showing operations of a terminal device;

FIG. 9 is a schematic flowchart showing operations relating to basestations;

FIG. 10 is a schematic flowchart illustrating operations of a terminaldevice;

FIG. 11 is a schematic flowchart illustrating operations of a basestation;

FIG. 12 schematically illustrates a system information data structure;

FIG. 13 is a schematic flowchart illustrating operations of a terminaldevice;

FIG. 14 is a schematic flowchart illustrating operations of a terminaldevice;

FIG. 15 is a summary flowchart of operations of a terminal device;

FIGS. 16 and 17 are summary flowcharts of operations of a base station;

FIGS. 18 to 21 are summary flowcharts illustrating operations of aterminal device; and

FIGS. 22 to 24 are summary flowcharts illustrating operations of a basestation.

DETAILED DESCRIPTION OF THE EMBODIMENTS

FIG. 1 provides a schematic diagram illustrating some basicfunctionality of a wireless telecommunications network/system 100operating in accordance with LTE principles. Various elements of FIG. 1and their respective modes of operation are well-known and defined inthe relevant standards administered by the 3GPP (RTM) body.

The network 100 includes a plurality of base stations 101 connected to acore network 102. Each base station provides a coverage area 103 (forexample, a cell) within which data can be communicated to and fromterminal devices 104. Data are transmitted from base stations 101 toterminal devices 104 within their respective coverage areas 103 via aradio downlink. Data are transmitted from terminal devices 104 to thebase stations 101 via a radio uplink. The core network 102 routes datato and from the terminal devices 104 via the respective base stations101 and provides functions such as authentication, mobility management,charging and so on. Terminal devices may also be referred to as mobilestations, user equipment (UE), user terminal, mobile radio, and soforth. Base stations may also be referred to as transceiverstations/nodeBs/e-NodeBs, and so forth.

Mobile telecommunications systems such as those arranged in accordancewith the 3GPP defined Long Term Evolution (LTE) architecture use anorthogonal frequency division multiplex (OFDM) based interface for theradio downlink (so-called OFDMA) and a single carrier frequency divisionmultiplex based interface for the radio uplink (so-called SC-FDMA). FIG.2 shows a schematic diagram illustrating an OFDM based LTE downlinkradio frame 201. The LTE downlink radio frame is transmitted from an LTEbase station (known as an enhanced Node B) and lasts 10 ms. The downlinkradio frame comprises ten subframes, each subframe lasting 1 ms. Aprimary synchronisation signal (PSS) and a secondary synchronisationsignal (SSS) are transmitted in the first and sixth subframes of the LTEframe. A physical broadcast channel (PBCH) is transmitted in the firstsubframe of the LTE frame.

FIG. 3 is a schematic diagram of a grid which illustrates the structureof an example conventional downlink LTE subframe (corresponding in thisexample to the first, i.e. left-most, subframe in the frame of FIG. 2).The subframe comprises a predetermined number of symbols which aretransmitted over a 1 ms period. Each symbol comprises a predeterminednumber of orthogonal sub-carriers distributed across the bandwidth ofthe downlink radio carrier.

The example subframe shown in FIG. 3 comprises 14 symbols and 1200sub-carriers spread across a 20 MHz bandwidth. The smallest allocationof user data for transmission in LTE is a resource block comprisingtwelve sub-carriers transmitted over one slot (0.5 subframe). Forclarity, in FIG. 3, each individual resource element (a resource elementcomprises a single symbol on a single subcarrier) is not shown, insteadeach individual box in the subframe grid corresponds to twelvesub-carriers transmitted on one symbol.

FIG. 3 shows resource allocations for four LTE terminals 340, 341, 342,343. For example, the resource allocation 342 for a first LTE terminal(UE1) extends over five blocks of twelve sub-carriers (60 sub-carriers),the resource allocation 343 for a second LTE terminal (UE2) extends oversix blocks of twelve sub-carriers and so on.

Control channel data are transmitted in a control region 300 (indicatedby dotted-shading in FIG. 3) of the subframe comprising the first nsymbols of the subframe where n can vary between one and three symbolsfor channel bandwidths of 3 MHz or greater and where n can vary betweentwo and four symbols for channel bandwidths of 1.4MHz. For the sake ofproviding a concrete example, the following description relates tocarriers with a channel bandwidth of 3 MHz or greater so the maximumvalue of n will be 3. The data transmitted in the control region 300includes data transmitted on the physical downlink control channel(PDCCH), the physical control format indicator channel (PCFICH) and thephysical HARQ indicator channel (PHICH).

PDCCH contains control data indicating which sub-carriers on whichsymbols of the subframe have been allocated to specific LTE terminals.Thus, the PDCCH data transmitted in the control region 300 of thesubframe shown in FIG. 3 would indicate that UE1 has been allocated theblock of resources identified by reference numeral 342, that UE2 hasbeen allocated the block of resources identified by reference numeral343, and so on.

PCFICH contains control data indicating the size of the control region(i.e. between one and three symbols).

PHICH contains HARQ (Hybrid Automatic Request) data indicating whetheror not previously transmitted uplink data has been successfully receivedby the network.

Symbols in a central band 310 of the time-frequency resource grid areused for the transmission of information including the primarysynchronisation signal (PSS), the secondary synchronisation signal (SSS)and the physical broadcast channel (PBCH). This central band 310 istypically 72 sub-carriers wide (corresponding to a transmissionbandwidth of 1.08 MHz). The PSS and SSS are synchronisation signals thatonce detected allow an LTE terminal device to achieve framesynchronisation and determine the cell identity of the enhanced Node Btransmitting the downlink signal. The PBCH carries information about thecell, comprising a master information block (MIB) that includesparameters that LTE terminals use to properly access the cell. Datatransmitted to individual LTE terminals on the physical downlink sharedchannel (PDSCH) can be transmitted in other resource elements of thesubframe.

FIG. 3 also shows a region of PDSCH containing system information andextending over a bandwidth of R344.

An LTE frame also includes reference signals which are not shown in FIG.3 in the interests of clarity.

FIG. 4 schematically illustrates a base station 101 in more detail. Thebase station 101 includes a transmitter (Tx) 400 for transmittingsignals via a wireless access interface (and via an antenna 430) to theone or more communications devices or UEs, and a receiver (Rx) 410 toreceive signals from the one or more terminal devices within thecoverage area of the base station. A controller 420 controls thetransmitter 400 and the receiver 410 to transmit and receive the signalsvia the wireless access interface. The transmitter 400 and receiver 410together form a transceiver. The controller 420 may perform a functionof controlling the allocation of communications resource elements of thewireless access interface and may in some examples include a schedulerfor scheduling transmissions via the wireless access interface for bothan uplink and the downlink. Operations of a base station discussed inconnection with the description below may be undertaken or overseen, atleast in part, by the controller 420. FIG. 4 therefore provides anexample of a base station for use in a wireless telecommunicationssystem, the base station comprising a transceiver 400, 410 configured toperform wireless communication with a terminal device; and a controller420 configured to control the transceiver.

In examples, the arrangement of FIG. 4 provides a base station for usein a wireless telecommunications system, the base station comprising: atransceiver (such as 400, 410) to perform wireless communication with aterminal device; and a controller (such as 420) to control thetransceiver to transmit system information defining communicationparameters and (as discussed below, for example as the area ID)identification data indicating a group of two or more base stationshaving at least part of the system information in common.

In other examples, it is not necessary for each base station to transmitthe system information (or all of the system information). Instead, abase station can transmit a reference to system information which theterminal device may already hold, such as system informationcorresponding to a neighbouring base station (so that there is at leasta good chance, especially in a system of small cells such as an array ofroad side units, that the terminal device will have already downloadedthe system information or—if not—that the terminal device will soon moveinto a cell corresponding to a base station which is transmitting thefull system information). The reference could be, for example, an areaID (see below) which is the same as the area ID of the neighbouringcell. Or the reference could be an indicator code, for example formed ofa preamble to show that it is an indicator code, followed by a data itemindicating a selection, amongst a set of possible sets or instances ofsystem information, which one should be used in connection with thatbase station. Or the reference could be a simple code saying “re-use(some or all of) whatever system information you currently hold” on thebasis that the terminal device's most recent interaction will have beenwith a geographically adjacent cell. Operating under arrangements suchas these, the base station of FIG. 4 provides an example of a basestation for use in a wireless telecommunications system, the basestation comprising: a transceiver to perform wireless communication witha terminal device; and a controller to control the transceiver totransmit reference data referencing a set of system information definingcommunication parameters of that base station; the controller beingconfigured to control the transceiver to conduct wireless communicationin accordance with the referenced system information.

FIG. 4, when operating in accordance with the principles and details setout below, provides an example of a base station for use in a wirelesstelecommunications system, the base station comprising: a transceiver toperform wireless communication with a terminal device; and a controllerto control the transceiver to transmit system information definingcommunication parameters and identification data indicating a group oftwo or more base stations having at least part of the system informationin common; in which: the system information comprises a plurality ofsystem information blocks; the controller is configured to control thetransceiver to transmit (i) a complete instance of a system informationblock; and (ii) a partial instance of the system information blockcontaining difference information with respect to an instance of systeminformation applicable to another base station.

FIG. 4, when operating in accordance with the principles and details setout below, provides an example of a base station for use in a wirelesstelecommunications system, the base station comprising: a transceiver toperform wireless communication with a terminal device; and a controllerto control the transceiver to transmit system information definingcommunication parameters; in which: the system information comprises aplurality of system information blocks; the controller is configured tocontrol the transceiver to transmit a timer reset message to instruct aterminal device to increase a remaining portion of a validity periodmaintained by that base station for system information held by that basestation.

FIG. 4, when operating in accordance with the principles and details setout below, provides an example of a base station for use in a wirelesstelecommunications system, the base station comprising: a transceiver toperform wireless communication with a terminal device; and a controllerto control the transceiver to transmit reference data referencing a setof system information defining communication parameters of that basestation; the controller being configured to control the transceiver toconduct wireless communication in accordance with the referenced systeminformation.

FIG. 5 schematically illustrates a terminal device 104 in more detail.The terminal device 104 includes a transmitter 500 associated with anantenna 530 for transmitting signals on the uplink of the wirelessaccess interface to the base station 101 and a receiver 510 forreceiving signals transmitted by the base station 101 on the downlinkvia the wireless access interface. The transmitter 500 and the receiver510 are controlled by a controller 520. The transmitter 500 and receiver510 together form a transceiver. Operations of a terminal devicediscussed in connection with the description below may be undertaken oroverseen, at least in part, by the controller 520. In some exampleembodiments of the present disclosure, the terminal device 104 is aso-called Low Complexity Machine Type Communication (LC-MTC) terminaldevice or narrowband internet-of-things (NB-IOT) device. NB-IOT devicesare used to connect various electronic and other items to a network suchas the internet. They are often characterised by low cost manufactureand deployment, low complexity, low power consumption and the like. Anexample of such device is smart electricity meter. Typical NB-IOTprovision is expected to occupy a low bandwidth, such as only 180 kHz ofbandwidth. FIG. 5 therefore provides an example of a terminal device foruse in a wireless telecommunications system, the terminal devicecomprising: a transceiver 500, 510 configured to perform wirelesscommunication with a base station; and a controller 520 configured tocontrol the transceiver.

The base station and the terminal device, as just described, can beimplemented, at least in part, by computer software which, when executedby a computer (such as a processor device acting as the controller ineach case), causes the computer to perform the described methods ofoperation. Such computer software may be provided by a non-transitorymachine readable storage medium storing the computer software.

The base station of FIG. 4 and the terminal device of FIG. 5, in thecontext of an arrangement such as that shown in FIG. 1, provide anexample of a telecommunications system comprising one or more suchterminal devices and one or more such base stations.

FIG. 5, when operating in accordance with the principles and details setout below, provides an example of a terminal device for use in awireless telecommunications system, the terminal device comprising: atransceiver to perform wireless communication with a base station and toobtain system information defining communication parameters from systeminformation data received from that base station; system informationstorage; and a controller to detect whether the system informationstorage already holds at least some of the system information applicableto a newly communicating base station and to control the transceiver toobtain any portions of the system information not already held by theterminal device, in which: the system information comprises a pluralityof system information blocks; and the controller is configured to detectparts of a system information block stored by the system informationstorage which are applicable to the newly communicating base station andto obtain other parts of that system information block as a partialsystem information block from the newly communicating base station.

FIG. 5, when operating in accordance with the principles and details setout below, provides an example of a terminal device for use in awireless telecommunications system, the terminal device comprising: atransceiver to perform wireless communication with a base station and toobtain system information defining communication parameters from systeminformation data comprising a plurality of information blocks; systeminformation storage; and a controller to detect whether the systeminformation storage already holds at least some of the systeminformation applicable to the newly communicating base station and tocontrol the transceiver to obtain any portions of the system informationfrom the newly communicating base station which are not already held bythe terminal device; in which the controller is configured to detectwhether identification data associated with information blockstransmitted by the newly communicating base station corresponds toidentification data associated with information blocks stored by thesystem information storage; in which the identification data comprisesarea information identifying a group of base stations and a value tagidentifying a version of one or more of the information blocks.

FIG. 5, when operating in accordance with the principles and details setout below, provides an example of a terminal device for use in awireless telecommunications system, the terminal device comprising: atransceiver to perform wireless communication with a base station and toobtain system information defining communication parameters from systeminformation data transmitted by that base station; system informationstorage configured to store the system information and one or moreassociated value tags identifying a version of respective portions ofthe system information; and a controller to detect whether the systeminformation storage already holds at least some of the systeminformation applicable to the newly communicating base station and tocontrol the transceiver to obtain any portions of the system informationnot already held by the terminal device from the base station; thecontroller being configured to detect an instruction to obtain updatedsystem information and, in response to detection of the instruction, toobtain from the base station an updated version of only those portionsof the system information having a value tag indicating a version ofthose portions different to the corresponding value tag held by thesystem information storage.

FIG. 5, when operating in accordance with the principles and details setout below, provides an example of a terminal device for use in awireless telecommunications system, the terminal device comprising: atransceiver to perform wireless communication with a base station and toobtain system information defining communication parameters from systeminformation data transmitted by that base station; system informationstorage; and a controller to detect whether the system informationstorage already holds at least some of the system information applicableto the newly communicating base station and to control the transceiverto obtain any portions of the system information not already held by theterminal device from the base station; the controller being configuredto maintain a validity timer indicating a validity period of the systeminformation and, in response to the end of the validity period, toobtain updated system information from the base station; the controllerbeing responsive to a timer reset message received from the base stationbefore the end of the validity period to alter the validity timer so asto increase a remaining portion of the validity period.

FIG. 6 is a schematic diagram showing a controller of a terminal devicesuch as the controller 520 of FIG. 5.

As discussed above, the controller is connected so as to controloperations of a transceiver (not shown in FIG. 6). The controllercomprises a detector 600, a comparator 610, a system information store620 and an operations controller 630. The detector 600 is arranged, inrespect of a newly acquired (newly communicating) base station, todetect so-called system information transmitted (for example, broadcast,though in other examples at least part of the communication could bedirected to a terminal device) by the base station. This is part of thearrangement by which the terminal device establishes communication withthe base station. The system information provides various communicationsparameters which are needed by the terminal device for suchcommunication.

The detector detects at a first stage a so-called Master InformationBlock (MIB). The MIB is the first piece of information which theterminal device acquires after it achieves downlink synchronisation witha base station. The MIB provides fundamental information which is neededfor the terminal device to obtain other information relating to thatbase station.

The MIB is transmitted according to a fixed schedule having aperiodicity of 40 ms, with multiple repetitions being made within the 40ms period. In some examples, the MIB can change at the 40ms period butis transmitted by the base station every 10ms within that period. TheMIB is detected first as it includes information relating to how theterminal device can receive the first of a set of system informationblocks (SIBs), and in particular the MIB provides information as to howto receive a first system information block (SIB1). For example, it mayrefer to scheduling information for the broadcast of SIB1.

In turn, the system information block SIB1 contains cell accessinformation as well as scheduling for other SIBs. The contents of thevarious system information blocks in example embodiments are given inthe following discussion.

Master Information Block (MIB)

As mentioned above, this is the first piece of information which theterminal device seeks to download after establishing downloadsynchronisation with a newly acquired (newly communicating) cell. Itcontains basic parameters defining the download channel and includesinformation required to receive SIB1.

SystemInformationBlockType1

This includes information relating to terminal device cell access anddefines the schedule of other SIBs. It is therefore needed before theother SIBs can be obtained.

SystemInformationBlockType2

The SystemInformationBlockType2 contains radio resource configurationinformation that is common for all terminal devices.

SystemInformationBlockType3

The SystemInformationBlockType3 contains cell re-selection informationcommon for intra-frequency, inter-frequency and/or inter-RAT cellre-selection.

SystemInformationBlockType4

The SystemInformationBlockType4 contains neighbouring cell relatedinformation relevant only for intra-frequency cell re-selection. The IEincludes cells with specific re-selection parameters as well asblacklisted cells.

-   SystemInformationBlockType5

The SystemInformationBlockType5 contains information relevant only forinter-frequency cell re-selection i.e. information about other E-UTRAfrequencies and inter-frequency neighbouring cells relevant for cellre-selection. The IE includes cell re-selection parameters common for afrequency as well as cell specific re-selection parameters.

Other SIBs

A similar concept can be applied to further SIBs. Those listed above arethe essential ones for NB-IOT, but for v2x case there may be furtherSIBs (e.g. SIB6 for inter-RAT mobility)

In other words, in examples, the system information comprises a masterinformation block, obtained by a terminal device before the terminaldevice obtains the system information blocks; the system informationblocks comprise a succession of a first system information block and oneor more further system information blocks; the master information blockprovides one or more parameters for reception of the first systeminformation block; and the first system information block provides oneor more parameters for reception of the one or more further systeminformation blocks.

The system information received from a base station can define one orboth of: (i) communication parameters for communication with that basestation; and (ii) communication parameters for communicating with otherterminal devices operating under the control of communication parametersreceived from that base station, in a device-to-device communicationoperation.

In examples, the system information data received from the base stationcan be system information data broadcast by the base station, forexample using a mechanism described above in connection with FIG. 3.

So, in the absence of any re-usable stored system information, a normaloperation of the detector 600 would be to detect first the MIB, then touse information from the MIB to detect SIB1, and then to use informationfrom SIB1 to detect the remaining SIBs.

In example embodiments of the present disclosure, the MIB and/or SIB1are associated with identification information which can be used todetect whether previously stored system information can be re-used forthe newly communicating base station. For example, the MIB and/or SIB1may contain the identification information (such as an area ID to bediscussed below). Or the identification information may beidentification information otherwise associated with the base station(such as a cell identifier or physical cell identifier (PCI)).

The comparator 610 compares identification information from the MIB orSIB1 with identification information applicable to system informationstored in the system information store 620. If the comparison ofidentification information indicates that some or all of the systeminformation stored in the system information store 620 can be used inconnection with the newly communicating base station, then thecomparator 610 instructs the detector 600 not to obtain those portionsof the system information which are being re-used from the systeminformation store. In some examples, a complete set of systeminformation may be reusable from the system information store 620. Inother examples, a subset of SIBs can be re-used. In other examples,parts of the contents of some SIBs can be re-used, and differentinformation indicating changes to certain aspects of the SIBs being usedfrom the system information store 620 is instead obtained by thedetector 600.

At the end of the process, whether that process involves a detector 600obtaining a complete set of new system information or some of the storedsystem information being re-used, the system information store 600 nowcontains a full set of system information applicable to the newlycommunicating base station. This system information is used by theoperations controller 630 to control operations of the terminal devicein connection with that base station.

Therefore, FIG. 6 (in conjunction with FIG. 5) provides an example of aterminal device for use in a wireless telecommunications system, theterminal device comprising: a transceiver (such as 500, 510) to performwireless communication with a base station and (for example, 600) toobtain system information defining communication parameters from systeminformation data received from that base station; system informationstorage (such as 620); and a controller (such as other functionality of520 as shown in FIG. 6) to detect whether the system information storagealready holds at least some of the system information applicable to thenewly communicating base station and to control the transceiver toobtain any portions of the system information not already held by theterminal device.

In FIG. 6, the controller is configured to detect (610) whetheridentification data associated with system information received from thenewly communicating base station corresponds to identification dataassociated with system information stored by the system informationstorage (620).

FIG. 7 schematically illustrates system information storage, for exampleby the system information store 620.

In some examples, the system information store 620 is arranged to storeonly one set of system information. This may be the system informationfrom a most-recently-accessed base station and in some examples, such asthose using an “area identifier”, this can be applicable to the newlycommunicating base station. However, in other embodiments, the systeminformation store 620 can store multiple sets of system information, andsuch an example is shown in FIG. 7. Here, each set 700, 710, 720 ofsystem information has one or more identifiers 730, 740, 750 associatedwith it. The identifiers can be compared with identification informationapplicable to a newly communicating base station to detect whether someor all of the system information 700, 710, 720 can be re-used.

FIG. 7 therefore provides an example of the system information storage620 being configured to store two or more instances of systeminformation (700, 710, 720), each instance corresponding to one or morerespective base stations. The instances can be, for example, two or moredistinct instances of system information most recently obtained by theterminal device. One or more of the instances may represent a part butnot all of the system information. An arrangement to handle this isdiscussed below with reference to FIG. 14.

As discussed above, in examples, the system information comprises aplurality of system information blocks; and the controller is configuredto detect whether the system information stored by the systeminformation storage provides system information representing some or allof the system information blocks applicable to the newly communicatingbase station.

FIG. 8 is a schematic flow chart illustrating operations of a terminaldevice. At a step 800, the device is powered on and selects a basestation or cell. At a step 810, the terminal device obtains and storesthe system information and an identifier for the selected base station.Operations then proceed involving communication with the selected cell.

Assume now that the terminal device is moved (its physical positionchanges) and, at a step 820 establishes communication with a new basestation or cell. At a step 830, the terminal device receives theidentifier information from the new cell (for example, as part of an MIBor SIB1 block). Then, at a step 840, the comparator 610 detects whetherthe received ID matches the ID associated with the stored systeminformation obtained at the step 810. If the answer is yes, then at astep 860 the terminal device simply uses the stored information ratherthan obtaining a further set of system information from the basestation. If the answer is no, then at a step 850 (similar to the step810) the terminal device obtains and stores system information and theID received at the step 830.

As discussed above, a hybrid of the steps 850, 860 can be used ininstances where the stored information and ID indicate that some but notall of the stored system information may be re-used. For example, thecontroller can be configured to detect parts of a system informationblock stored by the system information storage which are applicable tothe newly communicating base station and to obtain other parts of thatsystem information block from the newly communicating base station. Asan example, in response to reception of a first system information blockcarrying identification data which corresponds to system informationstored by the system information store, the controller is configured tocontrol the transceiver not to receive the further system informationblocks.

In some examples, the system information store 620 is configured tostore, as the identification data, a set of one of more base stationidentifiers applicable to at least respective portions of an instance ofstored system information. For example, the identifiers could beso-called value tags or information block tags indicating a selection,amongst a set of possible information block content, so that if analready-stored information block has a particular information block tag,and SIB1 (for example) indicates the information block tags of thefurther SIBs still to be broadcast, the terminal device can elect not toattempt to receive any further information blocks for which theinformation block tag matches the information block stag of acorresponding stored information block. In other examples, the store 620can store cell identifiers and/or public land mobile network identifiersand/or tracking area identifiers for which some or all of the storedinformation should be used. Accordingly, in examples, the identifierscan be cell identifiers; area identifiers; information block tags;tracking area identifiers; and/or public land mobile networkidentifiers.

Note also that the procedure of the steps 800, 810 could be replaced bya process whereby the terminal device retains, between uses, the mostrecently obtained system information in, for example, a non-volatilememory, or the terminal device is pre-loaded with a set of systeminformation.

In some examples, geographically nearby base stations have in common atleast some of their system information, so that if a terminal devicemoves from one such base station to another, there is either no need toobtain the system information again or there is a reduced need to obtainsystem information. One way in which this can be achieved is by the useof a so-called area identifier (area ID). The area ID can be transmittedby the base station as part of the MIB, as part of SIB1, as part ofanother small SIB transmitted before the transmission of SIB1, and soon. An example of this type of arrangement is illustrated in FIG. 9 inwhich operations relating to a group or cohort of base stations areshown. These operations can include: at a step 900, setting an area ID;at a step 910, associating cells or base stations (such as a group ofgeographically closely located base stations) with the area ID; and at astep 920, establishing a common set of system information, either all ofthe system information or selected portions of the system information,which is common to all base stations associated with that area ID. Thecommon set of system information can be passed to each base stationsharing the area ID via control channels of the core network 102 atsystem configuration.

The effect of the step 920 is that each of the base stations having thatarea ID operates according to communication parameters defined by thecommon system information. Also, as discussed above, the area ID istransmitted by the base stations in one of the existing blocks or as aseparate SIB such as an SIB transmitted before SIB1.

In the context of the cohort or set of base stations shown in FIG. 1,where the arrangement of FIG. 9 applies this provides an example of aset of two or more base stations, in which the identification data (suchas the area ID) and at least part of the system information are commonbetween the set of two or more base stations.

The arrangement of FIG. 9 can be used in the case where all of the basestations sharing the area ID have all of their system information incommon. In another example, a common, core, set of system information isdefined (for example amongst base stations sharing an area ID), with thepotential for individual base stations to broadcast differences withrespect to the common core system information. As an example of atechnique to achieve this, FIG. 10 shows steps carried out by a terminaldevice and FIG. 11 shows steps carried out by a base station.

FIG. 10 assumes that the terminal device already stores the common coreset of system information, either as an earlier download or aspre-loaded information. If it does not, then at a first operation (notshown in FIG. 10 but similar to the steps 800, 810 of FIG. 8) the commoncore system information is obtained from broadcast information the firstbase station accessed. Then, at a step 1000, the terminal device detectsthe area ID of an individual base station and receives difference dataat a step 1010 defining differences between the common core systeminformation defined in respect of that area ID and the particular systeminformation corresponding to that base station.

In FIG. 11, at a step 1100 a common core set of system information isdefined as discussed above, with application to multiple base stations.An individual base station defines any differences with respect to thecommon system information at a step 1110. Then, on a repetitive orcyclic basis, the individual base station transmits difference data at astep 1120 and, from time to time, a full set of the common systeminformation at a step 1130. This is an example of a base station inwhich the controller is configured to control the transceiver totransmit (i) a complete instance of the system information; and (ii) apartial instance of the system information containing differenceinformation with respect to an instance of system information applicableto another base station.

FIG. 12 schematically illustrates a system information data structureapplicable to the arrangement of FIGS. 10 and 11, in which an MIB 1200contains a pointer to SIB1 1210 which in turn contains a pointer tosubsequent SIBs 1220. Area ID information is provided in the MIB (1205)and/or in the SIB1 (1215). At least some of the SIBs (such as thesubsequent SIBs 1220) are considered as the common core systeminformation which is downloaded by a terminal device which does notcurrently hold a copy of that information. However, for a terminaldevice which does hold a copy of the common core information, the MIBand/or the SIB1 blocks provide reception information indicating how toreceive one or more difference SIBs 1230 (defining differences, if any,from the core information) which are received by the terminal device atthe step 1010 of FIG. 10.

The arrangement of FIG. 12, when transmitted by a base station (forexample using a format as shown in FIG. 3) provides an example of awireless data signal transmitted by a base station, the wireless datasignal comprising system information defining communication parametersand identification data (such as 1205, 1215) indicating a group of twoor more base stations having at least part of the system information incommon.

For example, the identification data (such as Area ID) many be carriedby one or both of the master information block and the first systeminformation block.

Embodiments of the disclosure provide other similar examples of awireless data signal transmitted by a base station, the wireless datasignal comprising system information blocks defining communicationparameters and identification data indicating a group of two or morebase stations having at least part of the system information in common,the system information blocks including (i) a complete instance of asystem information block; and (ii) a partial instance of the systeminformation block containing difference information with respect to aninstance of system information applicable to another base station; andas another example a wireless data signal transmitted by a base station,the wireless data signal comprising system information blocks definingcommunication parameters and, from time to time, a timer reset messageto instruct a terminal device to increase a remaining portion of avalidity period maintained by that base station for system informationheld by that base station.

FIG. 13 is a schematic flow chart illustrating operations of a terminaldevice under the arrangement of FIG. 12, in which at a step 1300 theterminal device detects the MIB and/or SIB1, and based on informationcontained in those blocks, at a step 1310 detects the difference SIB1230. At a step 1320 the terminal device stores the differences alongwith the area ID.

FIG. 14 is a schematic flow chart illustrating operations of a terminaldevice in order to manage the storage provided by the system informationstore 620.

At a step 1400 the terminal device receives system information blocksrelating to system information which is not currently held in the systeminformation store 620. At a step 1410, the terminal device detectswhether storage space is available in the system information store 620to store the newly receives system information. If the answer is yesthen the newly received system information and associated ID informationis stored at a step 1420. If, however, the answer is no then at a step1430 the least recently used (LRU) system information data in the systeminformation store 620 is deleted, and a step 1440 the newly receivedsystem information is stored along with its ID.

FIG. 15 is a flowchart providing a summary of a method of operation of aterminal device for use in a wireless telecommunications system andhaving a transceiver to perform wireless communication with a basestation and to obtain system information defining communicationparameters from system information data received from that base stationand system information storage; the method comprising:

detecting (at a step 1500) whether the system information storagealready holds at least some of the system information applicable to thenewly communicating base station; and

controlling (at a step 1510) the transceiver to obtain any portions ofthe system information not already held by the terminal device.

FIG. 16 is a flowchart providing a summary of a method of operation of abase station for use in a wireless telecommunications system and havinga transceiver to perform wireless communication with a terminal device;the method comprising:

controlling (at a step 1600) the transceiver to transmit systeminformation defining communication parameters and identification dataindicating a group of two or more base stations having at least part ofthe system information in common.

FIG. 17 is a flowchart providing a summary of a method of operation of abase station for use in a wireless telecommunications system and havinga transceiver to perform wireless communication with a terminal device;the method comprising:

controlling, at a step 1700, the transceiver to transmit reference datareferencing a set of system information defining communicationparameters of that base station; and

controlling, at a step 1710, the transceiver to conduct wirelesscommunication in accordance with the referenced system information.

Further respective examples of operations of the base station of FIG. 4and/or the terminal device of FIG. 5 will now be described. As anexample, the operations can be carried out by the respective controller420, 520, for example (though not necessarily) under software, firmwareor other program control.

FIG. 18 is a summary flowchart of a method of operation of a terminaldevice for use in a wireless telecommunications system, the methodcomprising:

obtaining (at a step 1800) system information defining communicationparameters from system information data received from a base station,the system information comprising a plurality of system informationblocks;

storing (at a step 1810) the system information;

detecting (at a step 1820) whether the system information storagealready holds at least some of the system information applicable to anewly communicating base station;

obtaining (at a step 1830) any portions of the system information notalready stored by detecting parts of a stored system information blockwhich are applicable to the newly communicating base station; and

obtaining (at a step 1840) other parts of that system information blockas a partial system information block (such as the difference SIB 1230discussed above) from the newly communicating base station.

This arrangement relates to the techniques discussed above withreference to FIGS. 12 and 13, in which one or more partial informationblocks are obtained from the base station. The content of the partialinformation blocks are then used (for example, at the step 1320discussed above) to replace or supplement the information alreadystored.

FIG. 19 is a summary flowchart of a method of operation of a terminaldevice for use in a wireless telecommunications system, the methodcomprising:

obtaining (at a step 1900) system information defining communicationparameters from system information data comprising a plurality ofinformation blocks;

storing (at a step 1910) the system information;

detecting (at a step 1920) whether the system information storagealready holds at least some of the system information applicable to anewly communicating base station;

obtaining (at a step 1930) any portions of the system information fromthe newly communicating base station which are not already stored; and

detecting (at a step 1940) whether identification data associated withinformation blocks transmitted by the newly communicating base stationcorresponds to identification data associated with stored informationblocks;

in which the identification data comprises area information identifyinga group of base stations and a value tag identifying a version of one ormore of the information blocks.

In this example, an information block tag or value tag is associatedwith each MIB and SIB and stored in the store 620 along with thecorresponding MIB or SIB. The area ID indicates the area of validity (asa group of base stations) of the value tag. The value tag can, in someexamples, indicate a version number or reference of the correspondingblock. On moving to a new base station, the controller of a terminaldevice compares the value tags and area ID of its stored MIB and SIBswith those of the corresponding blocks being provided by the new basestation and obtains only those blocks not having a match of both thearea ID and value tag.

For example, the group of base stations identified by the areainformation identifies those base stations to which the value tag isapplicable.

In examples, a respective value tag is associated with each of themaster information block, the first system information block and thefurther system information blocks.

FIG. 20 is a summary flowchart of a method of operation of a terminaldevice for use in a wireless telecommunications system, the methodcomprising:

obtaining (at a step 2000) system information defining communicationparameters from system information data transmitted by a base station;

storing (at a step 2010) the system information and one or moreassociated value tags identifying a version of respective portions ofthe system information; and

detecting (at a step 2020) whether the system information storagealready holds at least some of the system information applicable to thenewly communicating base station;

obtaining (at a step 2030) any portions of the system information notalready held by the terminal device from the base station;

detecting (at a step 2040) an instruction to obtain updated systeminformation; and

In response to detection of the instruction, obtaining (at a step 2050)from the base station an updated version of only those portions of thesystem information having a value tag indicating a version of thoseportions different to the corresponding stored value tag.

Here, the controller of the terminal device can use the value taginformation associated with stored MIB or SIBs so as to re-use any MIBor SIBs previously acquired which have a value tag (optionally, and anarea ID as discussed above) which matches those of the correspondingblocks being provided by the newly communicating base station. Inexamples, the value tag may indicate a version number or reference ofthe corresponding block.

In examples, the instruction is a paging instruction received from thebase station.

In examples, the instruction is included in the master information blockor the first system information block.

In examples, the controller is configured to maintain a validity timerindicating a validity period of the system information, the instructionbeing detected in response to the end of the validity period. Forexample, the controller can be responsive to a timer reset messagereceived from the base station before the end of the validity period toalter the validity timer so as to increase a remaining portion of thevalidity period. In examples, the controller is responsive to the timerreset message to reset the validity timer to indicate that full validityperiod is remaining. In examples, the timer reset message is a pagingmessage received from the base station.

FIG. 21 is a summary flowchart of a method of operation of a terminaldevice for use in a wireless telecommunications system, the methodcomprising:

obtaining (at a step 2100) system information defining communicationparameters from system information data transmitted by a base station;

storing (at a step 2110) the system information;

detecting (at a step 2120) whether the system information storagealready holds at least some of the system information applicable to thenewly communicating base station;

obtaining (at a step 2130) any portions of the system information notalready stored by the terminal device from the base station;

maintaining (at a step 2140) a validity timer indicating a validityperiod of the system information;

in response to the end of the validity period, obtaining (at a step2150) updated system information from the base station; and

in response to a timer reset message received from the base stationbefore the end of the validity period, altering (at a step 2160) thevalidity timer so as to increase a remaining portion of the validityperiod.

In this example, the terminal device maintains (for example, using thecontroller) a timer indicating a time towards a validity period forsystem information. An example of a validity period is three hours. Whenthe end of the validity period is reached, the terminal device obtainsreplacement system information from the base station. For a low powerdevice this could be unnecessary and/or inappropriate, especially if theblocks have not actually changed. This technique therefore allows thebase station to send a message or instruction to the terminal devicethat there is no need to update its system information.

In examples, in the altering step the timer reset message resets thevalidity timer to indicate that full validity period is remaining.

In examples, the timer reset message is a paging message received fromthe base station.

In examples, the timer reset message is included in a first systeminformation message received from the base station and the alteration tothe validity timer applies to one or more further system informationmessages.

In other examples, the controller is configured to infer the timer resetmessage from a first system information message received from the basestation for which the controller detects whether the system informationstorage already holds system information corresponding to that message,and the alteration to the validity timer applies to one or more furthersystem information messages.

FIG. 22 is a summary flowchart of a method of operation of a basestation for use in a wireless telecommunications system, the methodcomprising:

performing (at a step 2200) wireless communication with a terminaldevice; and

transmitting (at a step 2210) system information defining communicationparameters and identification data indicating a group of two or morebase stations having at least part of the system information in common,in which the system information comprises a plurality of systeminformation blocks, by transmitting (i) a complete instance of a systeminformation block; and (ii) a partial instance of the system informationblock containing difference information with respect to an instance ofsystem information applicable to another base station.

FIG. 23 is a summary flowchart of a method of operation of a basestation for use in a wireless telecommunications system, the methodcomprising:

performing (at a step 2300) wireless communication with a terminaldevice; and

transmitting (at a step 2310) system information defining communicationparameters, in which the system information comprises a plurality ofsystem information blocks; and

transmitting (at a step 2320) a timer reset message to instruct aterminal device to increase a remaining portion of a validity periodmaintained by that base station for system information held by that basestation.

FIG. 24 is a summary flowchart of a method of operation of a basestation for use in a wireless telecommunications system, the methodcomprising:

transmitting (at a step 2400) reference data referencing a set of systeminformation defining communication parameters of that base station; and

performing (at a step 2410) wireless communication with a terminaldevice in accordance with the referenced system information.

Finally, although the foregoing has described the terminal device asparticular examples, any type of device is envisaged. For example,according to present principles, the device may be a wearable devicesuch as smart glasses, or a fitness band. Further, the device may belocated in a vehicle such as a car or van or a boat, or it may be astationary device such as a smart meter, sensor or home appliance.

Where methods of processing, transmitting or receiving are discussedabove, it will be appreciated that apparatus configured to perform suchmethods are also considered to represent embodiments of the disclosure.

In so far as embodiments of the disclosure have been described as being(or are technically capable of being) implemented, at least in part, bysoftware-controlled data processing apparatus, it will be appreciatedthat a non-transitory machine-readable medium carrying such software,such as an optical disk, a magnetic disk, semiconductor memory or thelike, is also considered to represent an embodiment of the presentdisclosure.

It will be apparent that numerous modifications and variations of thepresent disclosure are possible in light of the above teachings. It istherefore to be understood that within the scope of the appended claims,the technology may be practiced otherwise than as specifically describedherein.

Embodiments of the present disclosure can be exemplified by thefollowing numbered paragraphs.

-   1. A terminal device for use in a wireless telecommunications    system, the terminal device comprising:

a transceiver to perform wireless communication with a base station andto obtain system information defining communication parameters fromsystem information data received from that base station;

system information storage; and

a controller to detect whether the system information storage alreadyholds at least some of the system information applicable to a newlycommunicating base station and to control the transceiver to obtain anyportions of the system information not already held by the terminaldevice, in which:

the system information comprises a plurality of system informationblocks; and

the controller is configured to detect parts of a system informationblock stored by the system information storage which are applicable tothe newly communicating base station and to obtain other parts of thatsystem information block as a partial system information block from thenewly communicating base station.

-   2. A terminal device according to clause 1, in which the controller    is configured to detect whether identification data associated with    system information received from the newly communicating base    station corresponds to identification data associated with system    information stored by the system information storage.-   3. A terminal device according to clause 1 or clause 2, in which the    system information storage is configured to store two or more    instances of system information, each instance corresponding to one    or more respective base stations.-   4. A terminal device according to clause 3, in which the system    information storage is configured to store two or more distinct    instances of system information most recently obtained by the    terminal device.-   5. A terminal device according to any one of the preceding clauses,    in which: the system information comprises a master information    block, obtained by a terminal device before the terminal device    obtains the system information blocks;

the system information blocks comprise a succession of a first systeminformation block and one or more further system information blocks;

the master information block provides one or more parameters forreception of the first system information block; and

the first system information block provides one or more parameters forreception of the one or more further system information blocks.

-   6. A terminal device according to clause 5, in which the    identification data is carried by one or both of the master    information block and the first system information block.-   7. A terminal device according to clause 5 or clause 6, in which, in    response to reception of a first system information block carrying    identification data which corresponds to system information stored    by the system information store, the controller is configured to    control the transceiver not to receive the further system    information blocks.-   8. A terminal device according to any one of clauses 2 to 7, in    which the system information storage is configured to store, as the    identification data, a set of one of more base station identifiers    applicable to at least respective portions of an instance of stored    system information.-   9. A terminal device according to clause 8, in which the base    station identifiers comprise one or more selected from the list    consisting of:

cell identifier;

area identifier;

information block tag;

tracking area identifier; and

public land mobile network identifier.

-   10. A terminal device according to any one of the preceding clauses,    in which the system information received from a base station defines    one or both of:

communication parameters for communication with that base station; and

communication parameters for communicating with other terminal devicesoperating under the control of communication parameters received fromthat base station, in a device-to-device communication operation.

-   11. A terminal device according to any one of the preceding clauses,    in which the system information data received from the base station    is system information data broadcast by the base station.-   12. A terminal device for use in a wireless telecommunications    system, the terminal device comprising:

a transceiver to perform wireless communication with a base station andto obtain system information defining communication parameters fromsystem information data comprising a plurality of information blocks;

system information storage; and

a controller to detect whether the system information storage alreadyholds at least some of the system information applicable to the newlycommunicating base station and to control the transceiver to obtain anyportions of the system information from the newly communicating basestation which are not already held by the terminal device;

in which the controller is configured to detect whether identificationdata associated with information blocks transmitted by the newlycommunicating base station corresponds to identification data associatedwith information blocks stored by the system information storage;

in which the identification data comprises area information identifyinga group of base stations and a value tag identifying a version of one ormore of the information blocks.

-   13. A terminal device according to clause 12, in which the group of    base stations identified by the area information identifies those    base stations to which the value tag is applicable.-   14. A terminal device according to clause 12 or clause 13, in which:

the system information comprises a master information block, obtained bya terminal device before the terminal device obtains the systeminformation blocks;

the system information blocks comprise a succession of a first systeminformation block and one or more further system information blocks;

the master information block provides one or more parameters forreception of the first system information block; and

the first system information block provides one or more parameters forreception of the one or more further system information blocks.

-   15. A terminal device according to clause 14, in which a respective    value tag is associated with each of the master information block,    the first system information block and the further system    information blocks.-   16. A terminal device for use in a wireless telecommunications    system, the terminal device comprising:

a transceiver to perform wireless communication with a base station andto obtain system information defining communication parameters fromsystem information data transmitted by that base station;

system information storage configured to store the system informationand one or more associated value tags identifying a version ofrespective portions of the system information; and

a controller to detect whether the system information storage alreadyholds at least some of the system information applicable to the newlycommunicating base station and to control the transceiver to obtain anyportions of the system information not already held by the terminaldevice from the base station;

the controller being configured to detect an instruction to obtainupdated system information and, in response to detection of theinstruction, to obtain from the base station an updated version of onlythose portions of the system information having a value tag indicating aversion of those portions different to the corresponding value tag heldby the system information storage.

-   17. A terminal device according to clause 16, in which the    instruction is a paging instruction received from the base station.-   18. A terminal device according to clause 16 or clause 17, in which:

the system information comprises a master information block, obtained bya terminal device before the terminal device obtains the systeminformation blocks;

the system information blocks comprise a succession of a first systeminformation block and one or more further system information blocks;

the master information block provides one or more parameters forreception of the first system information block; and

the first system information block provides one or more parameters forreception of the one or more further system information blocks.

-   19. A terminal device according to clause 18, in which the    instruction is included in the master information block or the first    system information block.-   20. A terminal device according to any one of clauses 16 to 19, in    which the controller is configured to maintain a validity timer    indicating a validity period of the system information, the    instruction being detected in response to the end of the validity    period.-   21. A terminal device according to clause 20, nd of the validity    period to alter the validity timer so as to increase a remaining    portion of the validity period.-   22. A terminal device according to clause 21, in which the    controller is responsive to the timer reset message to reset the    validity timer to indicate that full validity period is remaining.-   23. A terminal device according to clause 22, in which the timer    reset message is a paging message received from the base station.-   24. A terminal device for use in a wireless telecommunications    system, the terminal device comprising:

a transceiver to perform wireless communication with a base station andto obtain system information defining communication parameters fromsystem information data transmitted by that base station;

system information storage; and

a controller to detect whether the system information storage alreadyholds at least some of the system information applicable to the newlycommunicating base station and to control the transceiver to obtain anyportions of the system information not already held by the terminaldevice from the base station;

the controller being configured to maintain a validity timer indicatinga validity period of the system information and, in response to the endof the validity period, to obtain updated system information from thebase station;

the controller being responsive to a timer reset message received fromthe base station before the end of the validity period to alter thevalidity timer so as to increase a remaining portion of the validityperiod.

-   25. A terminal device according to clause 24, in which the    controller is responsive to the timer reset message to reset the    validity timer to indicate that full validity period is remaining.-   26. A terminal device according to clause 24 or clause 25, in which    the timer reset message is a paging message received from the base    station.-   27. A terminal device according to any one of clauses 24 to 26, in    which the timer reset message is included in a first system    information message received from the base station and the    alteration to the validity timer applies to one or more further    system information messages.-   28. A terminal device according to any one of clauses 24 to 26, in    which the controller is configured to infer the timer reset message    from a first system information message received from the base    station for which the controller detects whether the system    information storage already holds system information corresponding    to that message, and the alteration to the validity timer applies to    one or more further system information messages.-   29. A base station for use in a wireless telecommunications system,    the base station comprising:

a transceiver to perform wireless communication with a terminal device;and

a controller to control the transceiver to transmit system informationdefining communication parameters and identification data indicating agroup of two or more base stations having at least part of the systeminformation in common; in which:

the system information comprises a plurality of system informationblocks;

the controller is configured to control the transceiver to transmit (i)a complete instance of a system information block; and (ii) a partialinstance of the system information block containing differenceinformation with respect to an instance of system information applicableto another base station.

-   30. A base station according to clause 29, in which:

the system information comprises a master information block and two ormore system information blocks;

the system information blocks comprise a succession of a first systeminformation block and one or more further system information blocks;

the master information block provides one or more parameters forreception, by a terminal device, of the first system information block;and

the first system information block provides one or more parameters forreception, by a terminal device, of the one or more further systeminformation blocks.

-   31. A base station according to clause 30, in which the controller    is configured to control the transceiver to transmit the    identification data in one or both of the master information block    and the first system information block.-   32. A base station according to any one of clauses 29 to 31, in    which the controller is configured to control the transceiver to    broadcast the system information.-   33. A set of two or more base stations each according to any one of    clauses 29 to 32, in which the identification data and at least part    of the system information are common between the set of two or more    base stations.-   34. A base station for use in a wireless telecommunications system,    the base station comprising:

a transceiver to perform wireless communication with a terminal device;and

a controller to control the transceiver to transmit system informationdefining communication parameters; in which:

the system information comprises a plurality of system informationblocks;

the controller is configured to control the transceiver to transmit atimer reset message to instruct a terminal device to increase aremaining portion of a validity period maintained by that base stationfor system information held by that base station.

-   35. A base station for use in a wireless telecommunications system,    the base station comprising:

a transceiver to perform wireless communication with a terminal device;and

a controller to control the transceiver to transmit reference datareferencing a set of system information defining communicationparameters of that base station;

the controller being configured to control the transceiver to conductwireless communication in accordance with the referenced systeminformation.

-   36. A wireless data signal transmitted by a base station, the    wireless data signal comprising system information blocks defining    communication parameters and identification data indicating a group    of two or more base stations having at least part of the system    information in common, the system information blocks including (i) a    complete instance of a system information block; and (ii) a partial    instance of the system information block containing difference    information with respect to an instance of system information    applicable to another base station.-   37. A wireless data signal transmitted by a base station, the    wireless data signal comprising system information blocks defining    communication parameters and, from time to time, a timer reset    message to instruct a terminal device to increase a remaining    portion of a validity period maintained by that base station for    system information held by that base station.-   38. A method of operation of a terminal device for use in a wireless    telecommunications system, the method comprising:

obtaining system information defining communication parameters fromsystem information data received from a base station, the systeminformation comprising a plurality of system information blocks;

storing the system information;

detecting whether the system information storage already holds at leastsome of the system information applicable to a newly communicating basestation; and

obtaining any portions of the system information not already stored bydetecting parts of a stored system information block which areapplicable to the newly communicating base station and obtaining otherparts of that system information block as a partial system informationblock from the newly communicating base station.

-   39. Computer software which, when executed by a computer, causes the    computer to perform the method of clause 38.-   40. A machine-readable non-transitory storage medium which stores    computer software according to clause 39.-   41. A method of operation of a terminal device for use in a wireless    telecommunications system, the method comprising:

obtaining system information defining communication parameters fromsystem information data comprising a plurality of information blocks;

storing the system information;

detecting whether the system information storage already holds at leastsome of the system information applicable to a newly communicating basestation;

obtaining any portions of the system information from the newlycommunicating base station which are not already stored; and

detecting whether identification data associated with information blockstransmitted by the newly communicating base station corresponds toidentification data associated with stored information blocks;

in which the identification data comprises area information identifyinga group of base stations and a value tag identifying a version of one ormore of the information blocks.

-   42. Computer software which, when executed by a computer, causes the    computer to perform the method of clause 41.-   43. A machine-readable non-transitory storage medium which stores    computer software according to clause 42.-   44. A method of operation of a terminal device for use in a wireless    telecommunications system, the method comprising:

obtaining system information defining communication parameters fromsystem information data transmitted by a base station;

storing the system information and one or more associated value tagsidentifying a version of respective portions of the system information;and

detecting whether the system information storage already holds at leastsome of the system information applicable to the newly communicatingbase station;

obtaining any portions of the system information not already held by theterminal device from the base station;

detecting an instruction to obtain updated system information; and

in response to detection of the instruction, obtaining from the basestation an updated version of only those portions of the systeminformation having a value tag indicating a version of those portionsdifferent to the corresponding stored value tag.

-   45. Computer software which, when executed by a computer, causes the    computer to perform the method of clause 44.-   46. A machine-readable non-transitory storage medium which stores    computer software according to clause 45.-   47. A method of operation of a terminal device for use in a wireless    telecommunications system, the method comprising:

obtaining system information defining communication parameters fromsystem information data transmitted by a base station;

storing the system information;

detecting whether the system information storage already holds at leastsome of the system information applicable to the newly communicatingbase station;

obtaining any portions of the system information not already stored bythe terminal device from the base station;

maintaining a validity timer indicating a validity period of the systeminformation;

in response to the end of the validity period, obtaining updated systeminformation from the base station; and

in response to a timer reset message received from the base stationbefore the end of the validity period, altering the validity timer so asto increase a remaining portion of the validity period.

-   48. Computer software which, when executed by a computer, causes the    computer to perform the method of clause 47.-   49. A machine-readable non-transitory storage medium which stores    computer software according to clause 48.-   50. A method of operation of a base station for use in a wireless    telecommunications system, the method comprising:

performing wireless communication with a terminal device; and

transmitting system information defining communication parameters andidentification data indicating a group of two or more base stationshaving at least part of the system information in common, in which thesystem information comprises a plurality of system information blocks,by transmitting (i) a complete instance of a system information block;and (ii) a partial instance of the system information block containingdifference information with respect to an instance of system informationapplicable to another base station.

-   51. Computer software which, when executed by a computer, causes the    computer to perform the method of clause 50.-   52. A machine-readable non-transitory storage medium which stores    computer software according to clause 51.-   53. A method of operation of a base station for use in a wireless    telecommunications system, the method comprising:

performing wireless communication with a terminal device; and

transmitting system information defining communication parameters, inwhich the system information comprises a plurality of system informationblocks; and

transmitting a timer reset message to instruct a terminal device toincrease a remaining portion of a validity period maintained by thatbase station for system information held by that base station.

-   54. Computer software which, when executed by a computer, causes the    computer to perform the method of clause 53.-   55. A machine-readable non-transitory storage medium which stores    computer software according to clause 54.-   56. A method of operation of a base station for use in a wireless    telecommunications system, the method comprising:

transmitting reference data referencing a set of system informationdefining communication parameters of that base station; and

performing wireless communication with a terminal device in accordancewith the referenced system information.

-   57. Computer software which, when executed by a computer, causes the    computer to perform the method of clause 56.-   58. A machine-readable non-transitory storage medium which stores    computer software according to clause 57.

1. A method of operation of a terminal device for use in a wirelesstelecommunications system, the method comprising: obtaining systeminformation defining communication parameters from system informationdata received from a base station, the system information comprising aplurality of system information blocks; storing the system informationin memory; detecting whether the memory already holds at least some ofthe system information applicable to a newly communicating base station;and obtaining any portions of the system information not already storedin the memory by detecting parts of a stored system information blockwhich are applicable to the newly communicating base station andobtaining other parts of the system information block as a partialsystem information block from the newly communicating base station. 2.The method of claim 1, further comprising: determining whetheridentification data associated with system information received from thenewly communicating base station corresponds to identification dataassociated with system information stored by the memory.
 3. The methodof claim 1, further comprising: storing two or more instances of systeminformation, each instance corresponding to one or more respective basestations.
 4. The method of claim 3, further comprising: storing two ormore distinct instances of system information most recently obtained bythe terminal device.
 5. The method of claim 1, wherein the systeminformation comprises a master information block, obtained by theterminal device before the terminal device obtains the systeminformation blocks, the system information blocks comprise a successionof a first system information block and one or more further systeminformation blocks, the master information block provides one or moreparameters for reception of the first system information block, and thefirst system information block provides one or more parameters forreception of the one or more further system information blocks.
 6. Themethod of claim 5, wherein the identification data is carried by one orboth of the master information block and the first system informationblock.
 7. The method of claim 6, further comprising: in response toreception of a first system information block carrying identificationdata which corresponds to system information stored by the memory, notprocessing the further system information blocks.
 8. The method of claim2, further comprising: storing, as the identification data, a set of oneof more base station identifiers applicable to at least respectiveportions of an instance of stored system information.
 9. The method ofclaim 8, wherein the base station identifiers comprise one or moreselected from the list consisting of: a cell identifier; an areaidentifier; an information block tag; a tracking area identifier; and apublic land mobile network identifier.
 10. The method of claim 1,wherein the system information received from a base station defines oneor both of: communication parameters for communication with the basestation; and communication parameters for communicating with otherterminal devices operating under the control of communication parametersreceived from the base station in a device-to-device communicationoperation.
 11. The method of claim 1, wherein the system informationdata received from the base station is broadcast by the base station.12. A user equipment for use in a wireless telecommunications system,the user equipment comprising: a receiver configured to receive systeminformation defining communication parameters from system informationdata received from a base station, the system information comprising aplurality of system information blocks; a memory configured to store thesystem information; and a processor configured to determine whether thememory holds at least some of the system information applicable to anewly communicating base station; and control the receiver to obtainportions of the system information not already stored in the memory bydetecting parts of a stored system information block which areapplicable to the newly communicating base station, and obtaining otherparts of the system information block as a partial system informationblock from the newly communicating base station.
 13. The user equipmentof claim 12, wherein the processor is configured to determine whetheridentification data associated with system information received from thenewly communicating base station corresponds to identification dataassociated with system information stored by the memory.
 14. The userequipment of claim 12, wherein the memory is configured to store two ormore instances of system information, each instance corresponding to oneor more respective base stations.
 15. The user equipment of claim 14,wherein the memory is configured to store two or more distinct instancesof system information most recently obtained by the terminal device. 16.The user equipment of claim 12, wherein the system information comprisesa master information block, obtained by the user equipment before theuser equipment obtains the system information blocks, the systeminformation blocks comprise a succession of a first system informationblock and one or more further system information blocks, the masterinformation block provides one or more parameters for reception of thefirst system information block, and the first system information blockprovides one or more parameters for reception of the one or more furthersystem information blocks.
 17. The user equipment of claim 16, whereinthe identification data is carried by one or both of the masterinformation block and the first system information block.